Not Applicable
Not Applicable
The present invention relates to foams, and particularly foams manufactured to possess special purpose properties.
By way of background, there has been increasing interest in the development of foam products having specialized properties not found in conventional foams. One such property is magnetic responsiveness.
In the prior art, magnetically responsive foams have been produced by incorporating a metallic powder comprising ferromagnetic particles of relatively large size (e.g., 100-1500 micron iron particles) into a liquid phase foam system by way of mechanical impregnation during the foaming process. This approach is disclosed in U.S. Pat. No. 4,234,420 of Turbeville, which is directed to the manufacture and use of magnetically recoverable, oil sorbent foam particles for pollutant spill control. A disadvantage of this technique (as noted in the above-referenced patent) is that the metallic particles, depending on their size and abrasiveness, tend to cause varying amounts of disintegrative destruction of the foam over the course of multiple compression-recovery cycles. Furthermore, it has been observed by Applicant that the metallic particles are not well disbursed throughout the foam, and those particles which are at or near the surface of the foam tend to become readily dislodged from the foam matrix. These disadvantages may be acceptable if the foam is intended for use in granular or particulate form (such as for oil recovery), but there are many applications where requirements of foam structural integrity, uniform magnetic particle dispersion, and particle fastness/securement may preclude use of the above-described production technique.
Accordingly, an improved technique is needed for producing magnetically responsive foam. What is required is a magnetically responsive foam, and a manufacturing method therefor, in which the foam is imparted with magnetic properties, e.g., ferromagnetism, diamagnetism, paramagnetism, without the attendant disadvantages of the prior art approach described above.
It is an object of the present invention to provide an improved magnetically responsive foam and a foam manufacturing method therefor.
Another object of the present invention is to provide an improved magnetically responsive foam and a foam manufacturing method therefor wherein magnetically responsive material is incorporated into the foam in a manner that prevents the material from readily leeching out, even under harsh environmental conditions.
Still another object of the present invention is to provide an improved magnetically responsive foam and a foam manufacturing method therefor wherein magnetically responsive material is incorporated into the foam in a uniformly dispersed manner that does not impair the foam""s structural or functional properties.
Applicant has discovered that the foregoing objectives can be satisfied by a magnetically responsive foam having a three-dimensional cellular structure comprising the reaction product of a liquid phase foam system to which has been added a blowing agent and a magnetic fluid comprising a suspension of magnetically responsive particles in a liquid carrier. Applicant has observed, in particular, that by selecting an appropriate magnetic fluid and liquid phase foam system, the liquid carrier portion of the magnetic fluid appears to chemically react with one or more of the foam constituents, or a reaction product thereof, during the foaming chain reaction process, so as to become bound into the foam""s molecular structure. This tends to trap the magnetically responsive particles suspended in the liquid carrier, such that they do not readily leach out of the foam, even under adverse environmental conditions.
Suitable magnetic fluids include magnetorheological fluids and colloidal magnetic fluids (also known as ferrofluids). The magnetically responsive particles may comprise ferromagnetic material, diamagnetic material, paramagnetic material, etc., depending on the desired properties of the foam. Suitable liquid carriers include, but are not necessarily limited to, silicone-based, oil-based, and water-based liquid carrier systems. Suitable foam systems include, but are not necessarily limited to, polymeric foams, and particularly urethane foams, including non-hydrophilic and hydrophilic varieties thereof. The foams may be non-reticulated, or they may be subjected to a reticulation process to produce reticulated foams.
For urethane foams, the liquid phase foam system may include a polyol, an isocyanate or polyisocyanate, a catalyst and a surfactant. The blowing agent may be water that evolves into carbon dioxide upon addition to the liquid phase foam system. The catalyst may comprise any suitable urethane catalyst material, including amine catalysts and tin catalysts. The magnetic fluid may be incorporated at a weight ratio of between about 5-60 parts of the magnetic fluid to about 145 parts of a mixture of the polyol, the isocyanate or polyisocyanate, the blowing agent, the catalyst and the surfactant.
According to one exemplary embodiment of the invention, a mixture may be prepared which contains (by weight) about 100 parts polyol, about 29 parts isocyanate, about 28.5 parts magnetic fluid, about 3.5 parts water, about 0.3 parts silicone surfactant, and about 0.67 parts catalyst. Additionally, about 10.9 parts glycol may also be added. Many other embodiments of the invention may be produced by varying the nature and quantity of the ingredients that comprise the mixture.
Following mixing of the selected ingredients, a gaseous phase foam system is produced, which then conventionally cures into a solidified foam product having the magnetic fluid bound therein.